Process for concentrating nitric acid.



No. 887,266. WPATENTBDMAY' 12,1908.

H. PAULINE.

PROCESS FOR CONGENTRATING NITRIC ACID. APPLICATION FILED AUG. 18,1906

fiipecification oi Letters Patent.

ERMi NY :JQ'Zt CONCENTRATENG NIETRIU AGED.

Patented May 12, 1908.

Application filed August 13, 1986. Serial No. 330,387.

T all whom it may concern:

Be it known that l, HARRY lflmmnc, c

.sub'ec-t of the German Em Joror and resident .l v I provemcnts in Processes for {Toncentrcting Nitric Acid, 01 which the following is e specifioation.

Attempts have at ueous nitric acid by SlllJjJlJ-Llill of electrolysis with a View to c :entrating it at the anode or positive polo, but it has been ascertained by accurate experiments that the increase in conccntintio obtained in such case only amounted to o ht per-- centage over the original concentration, while by continuing the olectroly. the acid under tfieatnient 'hccanic dc nposcd, that is to say, converted into or gen and nitric oxide.

The present invention roia of this nature, and it is such t degree oi concentration, up t pure monohydratic acid ilN J can he ohtainod.

The invention consists, broadly, in passing the nitric oxids, formed at the cathode or negative pole by elcctrolyzing the aqueous nitric acid to be concentrated, into the acid surrounding the anode or positive pole, Where they dissolve and one oxidized by the oxygen generated at the anode, so as to form nitric acid, thus increasing the concentration of the anode compartment.

Other features will be understood from the following description, n 'erence hcinp; had to the accompanying drawing, which is e a grammatical View of an apparatus adopted for effecting the new process.

The apparatus represented. consists, in substance, of a U-tube a, I), :1 cross tube c establishing connnunicotion between the two legs thereof, and in such manner that one end of this tube extends into the interior of the leg (1, as shown, a feed tube f, and drain cocks g and c is the anode and d the cathode.

been made {0 concentrate it to a sort to processes h. t any desired The operation of this device is as follows. At the beginnhig of the process such an amount of the acid to be cmrceniiro ed plied to th apparatus the i liquid are just above the ele nearly so. l l ereupon elect c current is passed ijl'ilOd l'lgtllc liquid, 22' r the result that at the anode c oxygen is formed, while at the cathode d nitric oxide are generated. The letter pass through the tube c into the leg (4, where they dissolve in the nitric acid surrounding the anode, so as to he converted into nitric acid by the action of the oxygen. set free at the anode. After in the leg at e suitable or desired degree of concentration has been obtained, then the dilute nitric acid contained in. the log t is discharged through a cock This acid, which still contains a certain amount of nitric oxids, is thus separated from the oxidized concentrated one. it will be seen. that in this way it possible to produce an acid free of nitric oXids and in any desired concentration, and without the necessity of soy extra nianipulations. The said dilute acid may be got rid of the nitric oxids, contained therein, by heating; in, and may be roconductcd to its original degree of concentration by distilling it. Prccoution should be taken that on the one hand the degree of concentration at the cathode become not so low, and that on the other hand the current strength employed be not so high, that hydrogen is formed; on the contrary the mode of working must be such that only nitric dioxid and nitric oxid are set free.

The acid to be concentrated should by preference be subjected to a preliminary saturation with. nitric oxids in order that there maybe some oxidizable matter for the oxygen formed at the cathode, the object being to prevent such oxygen from escaping, through the tube c, toward the cathode in case the nitric acid at the latter be not yet saturated with nitric oXids to a degree sufiicicnt to enable these to escape, owing to their pressure, toward the anode, in the manner described. To aid in the production of nitric oxids the leg Z) may be heated at little.

has been found that it advantageous to conduct the nitric oxide into the ocid,'surrounding the anode, not in their gaseous condition, hut in a liquefied state, because in the latter condition they readily mix with the liquid at the anode, whereas gaseous nitric oxid is found to dissolve therein but with B. relatively great difficulty. in View of this fact it is advantageous to provide a cooling device of any suitable construction, which the nitric oxide on their slongthe tube 6 are caused to pass through so as to drop into the leg o. it is ,oi advantage in rot this case to maintain the leg I) at a constant temperature, such as some 30 01' 60 degrees centigrado.

x The chemical reaction accomplished in effecting the described process may be expressed by an equation such as the following:

N 0 is set free at the cathode, While H O is taken from the acid under treatment, this acid being an aqueous one, as stated.

What is claimed is: 1. The herein described process, consisting in electrolyzing a ueous nitric acid and pass- 111g the-nitric oxi s, formed at the cathode,

senses into the acid surrounding the anode, substanti ally as and for the purpose specified.

2. The herein described process, consisting in electrolyzing aqueous nitric acid, liquefying the nitrlc OXldS originated at the cathode, and in'passing such liquefied gases into 

